A flat panel display possesses advantages of being ultra thin, power saved and radiation free and has been widely utilized. Present flat panel displays mainly comprise a LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Display). Comparing with LCD, the active matrix OLED (Active-matrix organic light emitting diode, AMOLED) has numbers of advantages such as power consumption, color saturation, contrast, the application of the flexible, and widely used. However, threshold voltage will be drifted when TFT be stressed and high temperature for a long period during using. According to the different display image, the threshold voltage drift in each partial of panel will be different so that cause different brightness of display. In order to solve this problem, based on the original signal to add AMOLED inside compensation signal.